The present invention relates to an absorptivity detecting apparatus, a chromatographic apparatus, a method of detecting absorptivity and a method of chromatography.
Many absorptivity detecting apparatuses are used as detectors for liquid chromatographic apparatuses. The absorptivity detecting apparatus utilizes a phenomenon that a sample absorbs light having a specific wavelength, and detects characteristics of the ample by detecting a quantity of absorbed light of the specific wavelength (hereinafter referred to as "sample measurement wavelength"). That is, a quantity of a sample or the like is detected by comparing an intensity of incident light and an intensity of transmitted light. Such a technology is disclosed, for example, in Japanese Patent Application Laid-Open No. 3-226632.
In such a technology, it is known that an intensity of light emitted from a light source does not agree with an intensity of light incident to a sample. The reason is that light suffers effects such as change of refractive index and so on when the light is passing through the sample and passing through each element of an optical system. Therefore, by utilizing light having a wavelength which is less absorbed in the sample (hereinafter referred to as "reference wavelength"), an absorptivity is detected by comparing a detected value for the reference wavelength and a detected value for a detecting wavelength.
However, it has been found that absorptivity cannot be measured accurately unless the light source and the light intensity are stabilized. In general, it takes a long time to stabilize an intensity of a light source. Further, after stabilized, small change in light intensity of the light source cannot be inevitable. For example, measurement is continuously performed for several minutes to several hours at longest in a liquid chromatographic apparatus, and therefore an effect due to change in light intensity of the light source becomes large.